THE 
AMERICAN ALLIGATOR 


BY 


KARL P. SCHMIDT 
Assistant Curator of Reptiles and Amphibians 


FIELD MUSEUM OF NATURAL HISTORY 


CHICAGO 
1922 


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FIELD MUSEUM OF NATURAL HISTORY 
DEPARTMENT OF ZOOLOGY 
CHICAGO, 1922 


LEAFLET NuMBER 8 


The American Alligator 


The alligator is one of the best known of North 
American animals. Even in the northern states, its 
name and appearance are familiar to most people, 
whether through a picture post-card from a tourist 
friend in Florida, the sight of a souvenir baby 
“gator” or from a stuffed museum specimen. The 
name “alligator” is a corruption of the Spanish “El 
Lagarto,” which means “the lizard.” This term is 
still applied in some Spanish American countries to 
the crocodiles and caimans. 

The American alligator is an excellent example 
of the group of reptiles known technically as the 
Crocodilia. This group includes the gavials, croco- 
diles, alligators, and caimans, and a few related forms 
which have no common English names. The gavial 
(genus Gavialis), of which there is only one form or 
species, has an extremely long and slender snout, with 
a large number of slender, projecting teeth. The 
crocodiles (genus Crocodylus) include several species 
with more or less tapering snouts and with fewer 
teeth. 

Alligators and most caimans have broad shovel- 
shaped snouts, and differ from crocodiles in the posi- 
tion of the fourth lower tooth. 

These forms may be called, collectively, “croco- 
dilians.” In all, there are twenty known living species 
and many more fossil forms. They are often of 
great size, ugly and vicious in appearance, and wholly 
carnivorous. They inhabit fresh water swamps, lakes 


[25] 


2 FIELD MUSEUM OF NATURAL HISTORY 


and rivers in tropical or subtropical countries, though 
two species, the Nile Crocodile (which is found 
throughout Africa), and the East Indian Crocodile, 
are known to swim boldly out to sea. These two 
species are also notable as the most seriously danger- 
ous to human beings. They are all excellent and 
powerful swimmers and secure their food either in 
the water or from the neighboring banks. They are 
by no means exclusively aquatic, however, the true 
crocodiles, especially, being capable of active motion 
on land. All come ashore to sun themselves and to 
Ceposit their eggs. In size, the crocodilians are the 
largest of living reptiles. Some of the existing forms 
reach an occasional length of thirty feet, while the 
largest fossil forms are estimated at about fifty feet. 


The American alligator with a maximum adult 
size of about sixteen feet is intermediate between 
these monsters and the smallest forms. One of the 
South American caimans is not known to reach a 
length of more than four feet. 


Superficially, crocodiles resemble gigantic lizards, 
but with the exception of the general characters com- 
mon to all reptiles, they are really widely distinct 
from lizards. By their large size they remind us of 
extinct dinosaurs and examination of their skulls 
and skeletons shows that they are really more closely 
allied to the dinosaurs than to the other groups of 
living reptiles (turtles, lizards and snakes, and the 
Sphenodon of New Zealand). 


The fossil history of the Crocodilia is of great 
interest. Their mode of life insures the preservation: 
of their remains more frequently than is the case with 
more terrestrial animals, with the result that the 
record of their ancestry is rather better known than 
that of most groups of reptiles. They reached their 
greatest development toward the close of the great 


[ 26] 


THE AMERICAN ALLIGATOR 3 


age of reptiles, the direct ancestors of modern croco- 
diles and alligators being contemporaries of the 
dinosaurs, the flying reptiles, and the gigantic sea 
lizards of the late Cretaceous period. Just as might 
be expected from their semi-aquatic habits, we find 
that some of these ancestral forms had taken to 
marine life and become almost wholly aquatic, per- 
haps coming ashore only for egg-laying. 

There is great variation among the twenty 
living species of crocodilians in the length and breadth 
of the snout. The greatest degree of elongation of 


Fig 1. 

Skulls of Alligator (Alligator mississippiensis) Crocodile 
(Crocodylus americanus), and Gavial (Gavialis gangeticus), from 
left to right. 
the snout is shown by the Indian gavial (Gavialis 
gangeticus.) The Indian name, “gharial,” of which 
gavial is a corruption, means fish eater. Fish do in 
fact form the chief part of its food. They are caught 
by sudden sidewise lunges of the head and neck. In 
this movement a long slender snout offers much less 
resistance to the water than a broad one. The fre- 
quent tendency to elongation of the snout in other 


(27] 


4 FIELD MUSEUM OF NATURAL HISTORY 


crocodilians may be ascribed to similar habits and a 
similar need for mechanical efficiency. In the living 
forms (of the genus Crocodylus) this elongate snout 
is developed independently by three species, one in 
Australia, one in South America, and one in Central 
Africa. This is an example of what is called parallel 
evolution which is usually found in structures, like 
the slender snouts in question, definitely adapted to 
some special use. (Fig. 1). 

How to distinguish an alligator from a crocodile 
is a question frequently asked. The greater breadth 
of snout which characterizes the alligator is illus- 
trated above (in Fig. 1). The fourth lower tooth 
which is enlarged and fang-like in all crocodiles, fits 
into a pit inside the margin of the upper jaw in alli- 
gators and caimans, while in crocodiles it fits into a 
notch at the side of the upper jaw. From a side view, 
then, with the mouth closed, this enlarged tooth is 
concealed in alligators and caimans and visible in 
crocodiles. (Fig. 2). Alligators are distinguished 


ar ee 


Fig. 2. 
Side view of head of young American Alligator and Crocodile. 
Note the exposed lower tooth in the Crocodile. 


by a special bridge of bone dividing the nasal opening 
of the skull, which is absent in caimans and crocodiles. 

The appearance of the American alligator is fa- 
miliar to everyone. Alligators are probably adult at 
a length of about eight feet. They continue to grow, 
however, after reaching this size, so that very old 
specimens reach much larger dimensions. The 
largest recorded size may be placed at about fifteen 
feet, but even twelve-foot individuals are now ex- 


[23 ] 


THE AMERICAN ALLIGATOR 5 


tremely rare, owing to the destruction of the large 
specimens for their hides. Young alligators are dark 
brown or black with bright yellow cross-bands. The 
lighter markings become less and less distinct with 
age, and very old specimens are a dull dark gray or 
black. The large, regularly arranged, plate-like scales 
on the back are underlain by plates of bone in the skin. 
These bony plates are absent in the skin of the belly, 
which is, therefore, more valuable for leather. 
Caimans and the African dwarf crocodile (Osteolae- 
mus), have bony plates in the skin of the underparts, 
and in the caimans these plates are closely joined on 
the back and belly. Some fossil forms had an even 
more complete armor. The teeth are formidable. 
They are placed in regular sockets in the jaw-bones 
and are regularly shed, being replaced by new teeth 
growing into the hollow bases of the old ones. The 
head is remarkable for the nearly complete absence of 
flesh on its outer surface. There are no fleshy lips. 
The skin is so closely attached to the bone that it is 
impossible to detach it without destroying it. 

There are many adaptations to life in the water 
in the alligator’s body. The hind feet are fully 
webbed, the front feet slightly webbed. In active 
swimming, however, the legs are held at the sides and 
the body is propelled by sidewise strokes of the power- 
ful tail. The tail is strongly flattened from side to 
side and the ridge of scales along its upper edge in- 
creases the propelling surface. The form of the head 
is such that the alligator can float at the surface of the 
water with only eyes and nostrils exposed. The nos- 
trils can be closed by a valve-like flap of skin when it 
submerges. A similar arrangement of eyes and nos- 
trils is found in many other animals that live in the 
water, the hippopotamus being a notable example 
among mammals. A complicated apparatus provides 
for the opening of the mouth at the surface of the 

[29] 


6 FIELD MUSEUM OF NATURAL HISTORY 


water where food is usually seized, without inter- 
fering with breathing. A valve in the throat closes 
the gullet while a bony. palate separates the air cham- 
bers in the head from the mouth, the internal open- 
ing of the nostrils being at the very base of the skull 
instead of in the roof of the mouth, as in other rep- 
tiles. The gradual development of this bony palate 
can be traced in the fossil ancestry of the Crocodilia, 
and its progressive adaptation to special conditions 
is an impressive example of evolutionary change. . 
The American Alligator is found from the Rio 
Grande in Texas, in the streams and bayous of the 


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The distribution of living Alligators is shown in black on the 
map. The American Alligator (A) is found in southeastern North 
America; the Chinese Alligator (B), in eastern China. 


Gulf coastal plain, throughout Florida, and in the 
Atlantic coastal plain north to North Carolina. In 
the Mississippi, it ranges northward as far as the Red 
River. In former times it was abundant throughout 
its range, but hunting for skins and sport has made 
it scarce nearly everywhere. Possibly its most im- 
portant remaining strongholds are the Everglades of 
[30] 


THE AMEEICAN ALLIGATOR 7 


Florida and the Okefinokee Swamp of southern 
Georgia. 

Strangely enough, the only crocodilian which is 
closely enough related to the American alligator to 
be placed in the same genus by zoologists, is found in 
the Yang-tze River of eastern China. This is the 
small Chinese alligator (Alligator sinensis). This is 
less surprising when it is remembered that many of 
the most striking forms of animal and plant life in 
eastern North America have their nearest living rela- 
tives in China. This fact is illustrated by the tulip 
and sassafras among trees, the spoonbill sturgeon 
among fishes, and a number of common snakes and 
lizards besides the alligator, among reptiles. 

The food of the alligator consists largely of fish. 
The young probably eat crawfishes and other small 
animals as well, and as they increase in size, a few 
mammals that come to the water and a few water- 
birds are added to the diet. Large alligators are able 
to capture animals as large as a deer, dragging them 
under water to drown and tearing the victim to pieces, 
often with the aid of another alligator, before swal- 
lowing. The diet of even the largest specimens prob- 
ably consists chiefly of fish. The country inhabited 
by alligators is river-bottom land subject to overflow. 
During the spring floods, large numbers of fish find 
their way into the water-holes which are uncon- 
nected with the river at its normal level. As the 
season progresses and these holes dry out, the fish 
become more and more crowded and fall an easy prey 
to their enemies, among which the alligator is one of 
the most important, at least where it still occurs. 

Human beings are rarely attacked by alligators. 
Even where large specimens are found, the hunters 
and natives most familiar with the habits of “gators” 
have no fear of them and bathe in the waters in which 
they live. In this respect, alligators and caimans dif- 

[31] 


8 FIELD MUSEUM OF NATURAL HISTORY 


fer from crocodiles, which are much more active and 
dangerous animals, although the American crocodile 
is less to be feared than the African or East Indian 
species. 

Stones and pine knots are frequently found in the 
stomachs of alligators. Whether or not they are of 
any use in the digestion of food, like the pebbles in the 
gizard of the bird, is unknown. Many extinct reptiles 
are known to have made similar collections of “stomach 
stones.” The explanation of the hunters in the south, 
that they prevent the walls of the otherwise empty 
stomach from adhering during hibernation, is of 
course fanciful. Nearly everywhere in the United 
States, alligators hibernate for three or four months 
during the coldest part of the year. They bury them- 
selves in the mud of the water-holes or swamps in 
which they live, and remain dormant until the approach 
of spring brings them out. In some tropical countries 
where the climate becomes too dry for the native 
crocodilians, they “aestivate”’ during a few months of 
the hottest and dryest season, burying themselves in 
mud in the same way. 

After emergence from their winter sleep, alli- 
gators feed for a time before the beginning of the 
breeding season, which occupies the late spring 
months. During the mating season the bellowing of the 
males is heard, and from the frequent mutilations of 
large specimens, it is presumed that fighting takes 
place between them at this time. The voices may be 
heard at a distance of a mile or more. A strong musky 
odor is discharged from the scent-glands at the sides 
of the throat when they are excited. 

The female alligator prepares a nest for her eggs 
by biting off and carrying together a mass of vegeta- 
tion such as grass, cat-tails and rushes. In this way 
a rounded or conical pile of trash is built up, not unlike 
a muskrat’s nest, but placed at the edge or in the 


[ 32] 


THE AMERICAN ALLIGATOR 9 


neighborhood of the water. The pile is compacted by 
crawling back and forth over it. In this nest, the eggs, 
which average about thirty in number, are laid. The 
time of laying corresponds closely to the month of 
June, in Florida at least, and the hatching process 
occupies about eight weeks. The moist vegetation of 
the nest serves to prevent the drying out of the eggs 
and also protects them from the daily fluctuation in 
temperature. Possibly the heat from the decomposi- 
tion of the materials of the nest aids the development 
of the eggs. 

The mother alligator is said to guard the nest or 
at least to remain in its neighborhood during the de- 
velopment of the eggs, and at the time of hatching, she 
is supposed to assist the escape of the young by open- 
ing the nest. Unless this is the case, it is difficult to 
see how the young can force their way out, the mass 
of vegetation around the eggs having become very 
compact during the intervening time. There are no 
direct observations, of this habit, known to the writer. 
It is made very probable, however, by the existance of 
similar habits in the South American caimans and in 
the Nile Crocodile. It is well established that the 
latter animal digs the eggs out of the sand in which 
they are laid when the young are about to hatch, being - 
notified at the proper time by the loud calling of the 
young crocodiles within the eggs, whose voices may be 
heard at a distance of several yards. Unhatched alli- 
gators also are able to make themselves heard at a con- 
siderable distance. 

The newly hatched young are about eight inches 
long, while the average egg is about three inches in 
length. Their growth is fairly rapid. Specimens 
raised at the New York Zoological Society’s Reptile 
House reached a length of five and a half feet, and a 
weight of fifty pounds, at the age of five years. State- 
ments as to the extremely slow growth of alligators 

; [33] 


10 FIELD MUSEUM OF NATURAL HISTORY 


are based on stunted specimens, kept in water that is 
too cold for them, and insufficiently fed. They are 
able to live for a long time without food, but naturally 
cannot be expected to grow under unfavorable condi- 
tions. 

The use of alligator hides for leather has had a 
curious history. Not much use of alligator leather was 
made until 1855, when shoes and other objects made 
from it were in fashion for a brief season, and a few 
thousand skins were prepared. The leather went out of 
fashion again in a short time, but during the Civil War, 
the shortage of leather in the southern states led to a 
renewed demand for alligator skins, this time chiefly 
for boots and shoes. This use came to an end with 
the war, as the leather is really unsuited for shoes. 
The respite for the alligators, however, was a tempo- 
rary one, for the leather again became fashionable 
about 1896, for use in fancy slippers and boots, travel- 
ling bags, pocketbooks, music rolls, ete. Since that 
time, the demand for alligator skins has been a steady 
one. It has been found that the skin of the back, the 
so-called “horn back’, which was formerly discarded, 
can be tanned quite as well as that of the lower parts. 

The number of skins of crocodilians used in the 
United States, as estimated by the U. S. Fish Com- 
mission, was about 280,000, in 1902. This may be 
considered an average figure for the preceding period, 
but with the increasing scarcity of alligators, it has 
probably decreased considerably since then. Of this 
large number of skins, about 120,000 were those of 
American alligators, the remainder being chiefly 
crocodile skins from Mexico and Central America. 

Dr. A. H. Wright and W. D. Funkhouser, in their 
notes on the alligator in the Okefinokee Swamp, give 
a good account of what is probably the commonest 
method of hunting. They write: 

“The methods of hunting the alligator, as prac- 

[34] : 


THE AMERICAN ALLIGATOR ll 


ticed by the Lees and other inhabitants of the region, 
consist mainly of going out at night in small boats 
and locating the animals by means of a lamp fastened 
to the head of one hunter in the bow of the boat. An- 
other hunter in the stern paddles or poles and uses 
the sharp end of the push pole to ‘stick’ the body after 
the animal has been shot and has sunk to the bottom. 
According to these hunters, who every year take out a 
large number of skins, the eyes of the small alligators 
appear red by the light thus used, while those of the 
large specimens are yellow. The hunter carrying the 
light swings his head from side to side through an are 
of 180 degrees, and when an alligator is sighted, shoots 
it by the light of the lamp on his head. The common 
supposition that the skin of an alligator will turn the 
bullet of a gun is, of course, unfounded. Since, how- 
ever, only the head of the animal is usually exposed 
when it is in the water, they are commonly shot 
through the eyes. The hunters generally use a shot- 
_ gun loaded with buckshot. That a large number of 
alligators are annually secured in this manner is 
evidenced by the fact that the fields of the Lees are 
strewn with the skeletons and dorsal strips of skin 
which have been thrown away after each expedition. 
Only the ventral part of the skin is saved, the upper 
portions being too thick and spiny to admit of the 
primitive methods of tanning, and therefore, the crest 
and dorsal scales are not retained.” 

Alligators were formerly extremely numerous 
throughout their range, and their sluggish forms, 
eften mistaken for stranded logs, were a familiar sight 
on the banks of every body of water in the South. 
Steady hunting for their skins during the past sixty 
years, the robbing of their nests for eggs, the capture 
of large numbers of the newly hatched young for 
“souvenirs”, and wanton slaughter by so-called sports- 
men, have decimated the species to such an extent that 


[35] 


12 FIELD MUSEUM OF NATURAL HISTORY 


few places are now left where it can still be said to be 
abundant. Perhaps the most important of these 
refuges are parts of the Florida Everglades and the 
great Okefinokee Swamp of southern Georgia. In 
these places, at least for the present, the alligator is 
probably safe from extinction. The great interest 
that the animal has for naturalists and its importance 
as one of the most characteristic North American 
animals, make its growing scarcity a matter of regret 
to all nature lovers. 


The fact that the alligator is of such great interest 
to tourists (whether naturalists or not), may prove 
to be an important factor in saving the species from 
extinction. They seem to breed freely in captivity. 
The first “alligator farm” was established in 1895, and 
there are now at least eight “farms” in the United 
States. It would not be practicable to raise alligators 
for their skins alone, on account of their relatively 
slow rate of growth, but when the sale of baby alli- 
gators to tourists, the sale of larger specimens to 
zoological parks, and possibly an additional fee for 
visitors to the establishment are combined, the raising 
of alligators becomes a practical business. 


The capture of wild alligators, alive, is by no means 
an easy process. It is effected by means of noosing, or 
with a large hook placed on the end of a pole which is 
inserted into the alligator’s under-water retreat. The 
first farms where alligators were kept, were estab- 
lished primarily to accustom them to captivity and to 
taking food, preparatory to shipping them to zoolog- 
ical gardens, aquariums, and circuses. The demand 
for baby alligators for souvenirs led to the practice of 
hatching the eggs taken from the nests of wild alli- 
gators in incubators. This may be done by main- 
taining them at a temperature of 80 degrees F., and 
moistening them daily to prevent drying. Alligator 


[36] 


THE AMERICAN ALLIGATOR 13 


farms, however, proved to be a source of attraction 
for visitors, and at the larger of the modern estab- 
lishments, the number of alligators on hand runs up 
to several thousand, of which probably a few hun- 
dred are of breeding age. They are kept in enclosures 
of wire netting, with concrete lined pools or streams. 
They must be assorted somewhat according to size, 
and extremely large individuals are given separate 
pens. There seems to be no authentic account of their 
breeding habits in captivity, and observations on this 
point would be of great interest. Alligator farming 
appears to be a successful enterprise, for in 1921, in 
addition to adult specimens sold to zoological parks, a 
single farm in Jacksonville, Florida, sold over ten 
thousand baby alligators. 
KARL P. SCHMIDT, 
Assistant Curator of Reptiles and Amphibians. 


[37] 


14 FIELD MUSEUM OF NATURAL HISTORY 


Books and articles containing information about alligators. 


Barpour, THOMAS ....... A Note Regarding the Chinese Alligator 
(Proc. Acad. Nat. Sci. Phila., 1910, 
pp. 464-67) 


DitMars, R. L. ...........The Reptile Book. 
(New York, 1907) 


Dirmars, R. L. .........-. Reptiles of the World. 
(New York, 1910) 


HorRNADAY, WILLIAM T. ..The American Natural History. 
(London, 1904) 


REESE Ae Ms 3 odie caters ..-The Alligator and its Allies. 
(New York, 1915) 
SmitH, H. M. ..........Notes on the Alligator Industry. 


(Bulletin U. S. Fish Commission, 
XI, 1898, pp. 3438-45) 


WILLISTON, (Ss. Wor steiner Water Reptiles of the Past and Present. 
(Chicago, 1914) 


WricHt, A. H. and 
FUNKHAUSER, W. D..... A Biological Reconnaissance of the 
Okefinokée Swamp in Georgia. 
(Proc. Acad. Nat. Sci. Phila., 1915, 
pp. 136-39) 


Alligators and their allies are represented in the Field Museum 
by a large mounted alligator, figured as the frontispiece to this 
leafiet, a mounted gavial, and a caiman. In the hall of osteology 
are complete skeletons of the American Alligator, American croco- 
dile and the gavial. 


[38] 


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